Low RPM chip timing for faster spoolup.

[KEVINS]

OK guy's,
What are the theories for making a turbo hit max boost AS FAST AS POSSIBLE from an idle?

I was power braking my car into boost while recording it on DS and it was 34* around 2500rpm with maybe 5psi of boost.

To me I would think that less timing would help the engine rev quicker because the spark plug isn't firing so early forcing the piston back down AND more of the exhaust "flame/heat" would be heading out the exhaust valve sooner which would spool the turbo quicker.

What are the ideas reagarding low rpm timing for doing this? Why do chips have so much timing down low?
Anybody experiment with the low timing?

Doug J and I were sitting around last night trying to figure the theory on this but couldn't come up with anything significant.

Let's talk about this..
KS

 

[BM Computer Src]

The answer, or at least part of it is here:

http://www.bmcomputersource.com/ubb/Forum4/HTML/000006.html

We also put a picture of the timing table up for you to see.

-Bob

 

[KEVINS]

Thanks Bob.
Although I don't know ANYTHING about programming chips I was able to understand the table and compare it to my files which they seem to correspond. I did look closer at my DS files and I did notice that the timing was closer to 23-26 while under a steady load. It only spiked to 35 when I first started power braking it.

But, I'm a bit more interested in the theory of why even less timing wouldn't be better, say 10* with an LV8 of around 200 at 2500rpm? What would the result be with this type of programming? Would there only be drivabilty issues or ???

Thanks
KS

 

[GNandGS]

To me, to be THAT picky I would want to know if this was a boost builder "on the brake" or flat footin' it from a light. When dealing with track data this gets easier to play with as long as the method remains the same.

That said the concensus seems to be lower timing. There are so many exceptions though that I havent made up my mind. Wastegate method makes a big difference.

S

 

[BM Computer Src]

Well,
To tell you the truth, I have not tried going lower than I did with that table (like you ask, 10 degrees). The reason is becasue we are finding the spooling is now blowing off the drag radials. So, I'm reluctant to go looking for any spooling faster! The tests have been on a 89 TTA. Stock stuff, turbo/ic/inj. Any launch over 1 lb of boost, and upon coming out of the hole the drag radials will start to smoke from boost coming in so early/fast.

Also- something I did not state in the earlier post was that we put in combination the wastegate DC to 100% from the get go. There is no curve, or ramping in of the boost. It's more like on or off. This makes the boost goto max from as soon as possible. This combination of wastegate and timing has given the results I said above.

-Bob

 

[87GN_70GS]

Another thing to try is to set the wastegate coefficient to FF.

 

[GNandGS]

I didnt think we were talkin just stock configs...